JPH01208804A - Thin-film platinum temperature sensor - Google Patents

Abstract

PURPOSE:To manufacture a thin-film platinum temperature sensor excellent in thermal response speed, heat resistance and reliability at low cost by forming a sintered film mainly comprising a metallic alkoxide onto a substrate and shaping a platinum resistance thin-film and an electrode onto the sintered film. CONSTITUTION:A solution mainly comprising a metallic alkoxide is applied onto an alumina substrate 1 in 3mm width, 10mm length and 0.65mm thickness and baked at 150 deg.C, thus forming an electrical insulating baked film 2 having thickness of approximately 1mum and being composed of the mixed film of SiO2 and Al2O3. Platinum thin-films 3 in 0.5mum thickness are attached through a sputtering method, leads 6 are fitted to extraction electrodes 4 and the thin-films 3 and the leads 6 are coated with a protective film 5 consisting of SiO2. Since the baked film 2 is composed of minerals, has uniform film thickness and shapes a smooth surface, a low-cost substrate, which has excellent heat resistance and thermal conductivity and the irregularities of the surface of which are increased, can be used, and the mixing of an impurity to the platinum films cam be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thin film platinum temperature sensor used in automobiles, home appliances, industrial instruments, and the like.

Conventional technology Conventional temperature sensors can be roughly divided into those that have high accuracy but are expensive and cumbersome to handle, and those that are simple and can be used in large quantities but have low accuracy. There is.

However, with recent rapid advances in electronics, there has been a demand for temperature sensors that are robust, can be used in large quantities, and have high accuracy, especially precision temperature sensors for automobiles. In particular, for automobiles, there is a need for something that is inexpensive, compact, highly accurate, has a wide temperature range, exhibits a linear resistance change, is strong against vibrations, and has good thermal responsiveness. Conventionally, a platinum side temperature resistor has been used as a precision temperature sensor, but since the platinum wire is used, the resistance value is low at 50Ω or 100Ω, which makes the peripheral circuit complicated and noise from the peripheral circuit. There is a problem that it is susceptible to the effects of vibration, and it is also large in size and is also susceptible to vibration and shock. Furthermore, since there is a limit to how thin platinum wire can be made, a considerable amount of expensive platinum wire is used, and mass production is difficult because the platinum wire is wound one by one around a ceramic bobbin. This would have been impossible and quite expensive.

In order to solve these problems, temperature sensors have been developed that use thick or thin platinum films instead of platinum wires. However, thick film platinum temperature sensors have drawbacks such as difficulty in forming fine patterns of 100 μm or less using screen printing technology and large manufacturing variations.

On the other hand, thin-film platinum temperature sensors can be miniaturized because the pattern can be easily made finer, and they can also be made more sensitive due to higher resistance.Furthermore, they have strong mechanical strength, and can be mass-produced by reducing variations through wafer processing. It has advantages such as being suitable for

Problems to be Solved by the Invention As a manufacturing method for a thin film platinum temperature sensor, first, a thin platinum film with a thickness of several thousand layers is deposited on an insulating substrate by vacuum evaporation, sputtering, etc., and then wet etching or sputter etching. A fine pattern is formed by a method such as a method such as a method, and heat treatment is performed at a high temperature of 900 to 1000° C. in the atmosphere. After that, the resistance value is adjusted by trimming, the lead wire is taken out, and a protective film is coated. At this time, an alumina substrate or the like is used as the insulating substrate. However, in order to form a fine pattern of platinum thin film on an alumina substrate, it is necessary to smooth the substrate surface. For this purpose, it is necessary to use a high-purity alumina substrate for thin films or an alumina substrate whose surface has been polished, which has the disadvantage that the substrate becomes expensive. On the other hand, there is a method of coating an alumina substrate with a glass glaze, but the heat resistance of the glass glaze is at most 900'C, which is low and there is concern that impurities may be mixed into the platinum film. Moreover, the glass glaze layer is thick, 10 to 30 μm, and the heat conduction of the substrate is poor, so there is also a drawback that the thermal response of the sensor is poor.

As mentioned above, conventional substrate materials have many problems.

The present invention solves these problems, and aims to provide a thin film platinum temperature sensor that has a fast thermal response speed, good heat resistance, and excellent reliability at a low cost.

Means for Solving the Problems In order to solve these problems, the present invention forms an electrically insulating fired film containing a metal alkoxide as a main component on a substrate, and forms a platinum resistive thin film and an electrode thereon. It is characterized by:

Function: By forming the above-mentioned metal alkoxide fired film, a smooth substrate surface can be obtained, a fine pattern of platinum thin film can be formed, and the platinum film has good thermal conductivity, high heat resistance, and chemical stability. The amount of impurities mixed into the thin film is reduced,
Problems such as board price, thermal response, heat resistance, and reliability are resolved.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In the figure, 1 has a width of 3M, a length of 10M, and a thickness of 0.65
MM is an alumina substrate, and 2 is alumina substrate 1 coated with a solution containing metal alkoxide as a main component.
This is an electrically insulating fired film made of a mixed film of 5in2 and Mu 1203 with a thickness of about 1 μm formed by firing at a temperature of 120°C. Furthermore, 3 was made with p by sputtering method.
A platinum resistive thin film is deposited with a thickness of about 0.5 μm and patterned by sputter etching, 4 is an electrode for leading out a lead wire connected to this platinum resistive thin film 3, and 6 is a 5in2 electrode that covers the platinum resistive thin film. It is a protective film.

Further, 6 is a lead wire connected to the electrode 4.

The alumina substrate used in this example is made of a commonly used, low-cost material with a purity of 96 yen, and has an uneven surface roughness of 2 to 3 μm. However, after coating and firing the metal alkoxide, the surface roughness of the substrate was less than 0.2 μm, which was the same level of smooth surface as an expensive alumina substrate for thin films with a purity of 99.51%. .

Furthermore, since the fired metal alkoxide film is inorganic and can form a thin film with a uniform thickness, it has excellent heat resistance, reduces the amount of impurities mixed into the platinum film, and has good thermal conductivity. The thermal time constant of the temperature sensor in this example is until it reaches a resistance value equivalent to 63.2% of the temperature difference between 20°C and 100'C when the temperature sensor is moved from 20°C to 100°C. When I measured the time, it was about 0.8116
The thermal response was approximately 1/2 that of the one using an alumina substrate coated with 0 and glass glaze, and the thermal response was significantly improved.

The fired metal alkoxide film of this example was 5.
Although a mixed film of 102 and 1205 was used, it is also possible to use 1203 alone or other fired films of metal alkoxides.

Further, the substrate may be made of materials other than alumina, and materials without electrical insulation such as metal can also be used.

Effects of the Invention As described above, according to the present invention, since a fired metal alkoxide film is used as an electrical insulating film on a substrate, a thin film platinum temperature sensor has the following properties: (1) Good thermal response (2) Excellent heat resistance (3) Excellent reliability (4) Low cost and other effects can be obtained.

[Brief explanation of the drawing]

The figure is a sectional view of a thin film platinum temperature sensor according to an embodiment of the present invention. 1... Alumina substrate, 2... Fired film,
3...Platinum thin film, 4...Electrode, 6.Old...Protective film, 6.Old...Lead wire.

Claims (1)

[Claims] A thin film platinum temperature film characterized in that an electrically insulating fired film is formed by applying a solution containing a metal alkoxide as a main component onto a substrate and firing it, and a platinum resistive thin film and an electrode are formed on this fired film. sensor.